Don’t Mess with a Geophysicist’s House: A Case Study of Ground Penetrating Radar (3D) for Concrete Moisture Mapping and Void Detection in the Saturated Soil beneath the Concrete Foundation
Environmental Geophysics Associates, 2000 Cullen Ave., Ste. 7, Austin, Texas 78757
Texas has large areas, including Houston, with clayey soils that shrink and swell with changes in soil moisture content. This shrinking and swelling may cause movement of residential foundations that adversely affects the residence. Different levels of moisture around the perimeter and under the buildings can create voids, upheavals, slumping, and other foundation problems.
Clayey soil is present throughout the area where the subject residence is located in the northwest part of Houston. This type of soil expands when it gets wet, and shrinks as it dries.
The house is 8 years old and the the homeowner replaced the carpets in the living room with wood flooring about one year after they moved in. The wood floor started showing discoloring within 3 months after they were installed.
An engineering company was contracted to evaluate the moisture problem in the living room. However, results from the plumbing and engineering studies of the mechanicals could neither pinpoint the source of the moisture specifically nor the conditions of the concrete slab and the soil beneath it. To address the problem, the homeowner hired his own geophysical company to perform ground penetrating radar surveys in the living room.
Ground penetrating radar (GPR) results indicate a significant void beneath the concrete foundation, two post-tension cables (PTC) within the concrete and a moderate ‘anomaly,’ that correlates well with the discolored, moisture-affected areas of the wood floor This correlation suggests that moisture wicking through the concrete foundation at the disintegrated PTC could have cause the water damage in the living space.
AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012